View source for Immittance

{{Short description|Combined measure of impedance and admittance.}}
{{Distinguish|Emittance (disambiguation){{!}}Emittance}}

{{Infobox physical quantity
| name       = Immittance
| width      =
| background =
| image      = File:Gray920.png
| caption    = Combined measure of impedance, admittance, or both. Immittance is crucial to several practices, such as [[tympanometry]].
| unit       = N/A
| symbols    = {{math|W}}, {{math|Z<sub>a</sub>}}, {{math|Y<sub>a</sub>}},<ref name=Lilly>{{Cite journal |last=Lilly |first=David |date=2005-04-20 |title=The Evolution of Aural Acoustic-Immittance Measurements |url=http://pubs.asha.org/doi/10.1044/leader.FTR2.10052005.6 |journal=The ASHA Leader |language=en |volume=10 |issue=5 |pages=6–24 |doi=10.1044/leader.FTR2.10052005.6 |issn=1085-9586|url-access=subscription }}</ref> {{math|C}}, {{math|F}}, {{math|t}}, {{math|∈}}, {{math|ℝ}}, {{math|jt}}, {{math|ϵ}}, {{math|χ}}, {{math|M}}<ref>{{Cite journal |last=Malkow |first=Dr. Ing T |date=27 September 2017 |title=Immittance Data Validation by Kramers‐Kronig Relations – Derivation and Implications |journal=ChemElectroChem |volume=4 |issue=11 |pages=2777–2782 |doi=10.1002/celc.201700630 |pmid=29577007 |pmc=5861665 }}</ref>
| baseunits  = 
| dimension  = wikidata
}}

'''Immittance''' is a term used within [[electrical engineering]] and [[acoustics]], specifically [[bioacoustics]] and the [[inner ear]], to describe the combined measure of [[admittance|electrical]] or [[acoustic admittance]] and [[Electrical impedance|electrical]] or [[acoustic impedance]]. Immittance was initially coined by [[Hendrik Wade Bode|H.&nbsp;W.&nbsp;Bode]] in 1945, and was first used to describe the electrical admittance or impedance of either a [[Node (circuits)|nodal]] or a [[Mesh analysis|mesh]] network. Bode also suggested the name "adpedence", however the current name was more widely adopted. In bioacoustics, immittance is typically used to help define the characteristics of noise reverberation within the middle ear and assist with [[differential diagnosis]] of middle-ear disease.<ref name=Lilly /> Immittance is typically a [[complex number]] which can represent either or both the impedance and the admittance (ratio of [[volt]]age to [[Electric current|current]] or vice versa in electrical circuits, or volume velocity to [[sound pressure]] or vice versa in acoustical systems) of a system.<ref>{{Cite web |last=Scanlan |first=J. O. |date=2020 |title=Immittance |url=https://www.accessscience.com/content/article/a337950 |access-date=2023-05-20 |website=McGraw Hill's AccessScience |language=en}}</ref> 
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Immittance does not have an associated unit because it applies to both impedance, which is measured in [[ohm]]s ({{math|Ω}}) or [[acoustic ohm]]s, and admittance, which is commonly measured in [[Siemens (unit)|siemens]] ({{math|S}}) and historically has also been measured in [[mho]]s ({{math|℧}}), the [[Multiplicative inverse|reciprocal]] of ohms.

==Notable usage==

===Bioacoustics===
In [[audiology]], [[tympanometry]] is sometimes referred to as ''immittance testing''. Tympanometry is especially effective when both the impedance and admittance of the inner ear are accounted for. Immittance allows for the analysis of both, and therefore is crucial to multiple-component, multiple-frequency tympanometry. Clinically, few cases require the use of this technique for accurate diagnosis; but for the fewer than 20% of cases which do require it, the technique is a necessity.  Multiple-component, multiple-frequency tympanometry is invaluable for the differential diagnosis of fixation of the lateral [[Ossicles|ossicular chain]] from fixation of the [[stapes]], profound [[Conductive hearing loss|mixed hearing losses]], clinical [[otosclerosis]] from disruption of the ossicular chain, [[hypermobility (joints)|hypermobility]] of the [[incudostapedial joint]], and congenital ossicular fixation in children.<ref>{{Cite web |last1=Sacramento |first1=Sacramento ENT 1111 Exposition Blvd |last2=Office:736-3399 |first2=CA 95815 |title=Immittance Testing |url=https://sacent.com/services/ent-procedures/ears-hearing/audiological-evaluation-testing/immittance-testing/ |access-date=2023-05-20 |website=Sacramento ENT |language=en-US}}</ref>

===Electrical engineering===
In electronics, an immittance [[Smith chart]] can be created by overlaying both the impedance and admittance grids, which is useful for cascading series-connected with parallel-connected electric circuits. This allows for the visualization of changes in impedance or admittance in the system caused by components of either the series or parallel circuit.<ref>{{Cite web |title=The Immittance Smith Chart - Impedance Matching with only L and C |url=https://www.antenna-theory.com/tutorial/smith/smithchartA.php |access-date=2023-05-20 |website=www.antenna-theory.com}}</ref>

==External links==
{{Wiktionary|immittance}}
* [https://archive.org/details/dli.ernet.15701/page/15/mode/2up Network Analysis and Feedback Amplifier Design (H. W. Bode, 1945)]

==References==
<references/>

[[Category:Physical quantities]]
[[Category:Electrical parameters]]